U.S. patent number 5,981,044 [Application Number 08/712,767] was granted by the patent office on 1999-11-09 for multi-layered tissue paper web comprising biodegradable chemical softening compositions and binder materials and process for making the same.
This patent grant is currently assigned to The Procter & Gamble Company. Invention is credited to Bart Steven Hersko, Dean Van Phan, Paul Dennis Trokhan.
United States Patent |
5,981,044 |
Phan , et al. |
November 9, 1999 |
**Please see images for:
( Certificate of Correction ) ** |
Multi-layered tissue paper web comprising biodegradable chemical
softening compositions and binder materials and process for making
the same
Abstract
Multi-layered tissue paper webs comprising biodegradable
chemical softener compositions and binder materials are disclosed.
The multi-layered tissue webs are useful in the manufacture of
soft, absorbent paper products such as facial tissues and/or toilet
tissues. The multi-layered tissue paper products contain a
biodegradable chemical softening composition, preferably comprising
a mixture of an ester-functional quaternary ammonium compound and a
polyhydroxy compound. The multi-layered tissue paper webs also
contain an effective amount of binder materials to control linting
and/or to offset the loss in tensile strength, if any, resulting
from the use of the chemical softening compositions. Preferably,
the majority of the biodegradable chemical softening compositions
will be disposed on the outer layers of the multi-layered tissue
paper products where they are most effective at enhancing softness.
The majority of the binder materials are also preferably disposed
on the outer layers of the multi-layered product to control
linting.
Inventors: |
Phan; Dean Van (West Chester,
OH), Trokhan; Paul Dennis (Hamilton, OH), Hersko; Bart
Steven (Cincinnati, OH) |
Assignee: |
The Procter & Gamble
Company (Cincinnati, OH)
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Family
ID: |
27375068 |
Appl.
No.: |
08/712,767 |
Filed: |
September 12, 1996 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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376541 |
Jan 20, 1995 |
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085852 |
Jun 30, 1993 |
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085435 |
Jun 30, 1993 |
5405501 |
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Current U.S.
Class: |
428/212; 162/127;
162/129; 162/130; 162/147; 162/149; 428/220; 428/332 |
Current CPC
Class: |
D21H
17/06 (20130101); D21H 17/07 (20130101); D21H
17/14 (20130101); D21H 21/22 (20130101); D21H
27/38 (20130101); D21H 17/54 (20130101); Y10T
428/26 (20150115); Y10T 428/24942 (20150115) |
Current International
Class: |
D21H
17/06 (20060101); D21H 27/30 (20060101); D21H
17/54 (20060101); D21H 17/07 (20060101); D21H
17/00 (20060101); D21H 17/14 (20060101); D21H
27/38 (20060101); D21H 21/22 (20060101); D21H
021/22 () |
Field of
Search: |
;428/212,220,332
;162/127,112,129,130,141,147,149,158 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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61-308312 |
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Jul 1988 |
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JP |
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4-100995 |
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Apr 1992 |
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JP |
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Other References
"Applications of Armak Quaternary Ammonium Salts", Bulletin 76-17,
Armak Co., (1977)..
|
Primary Examiner: Davis; Jenna
Attorney, Agent or Firm: Hersko; Bart S. Milbrada; Edward J.
Linman; E. Kelly
Parent Case Text
This is a continuation-in-part of application Ser. No. 08/376,541,
filed on Jan. 20, 1995, abandoned; which is a continuation of
application Ser. No. 08/085,852, abandoned; filed on Jun. 30, 1993;
and a continuation-in-part of application Ser. No. 08/085,435,
filed on Jun. 30, 1993, U.S. Pat. No. 5,405,501.
Claims
What is claimed is:
1. A multi-layered tissue paper web comprising three superposed
layers, an inner layer and two outer layers, said inner layer being
located between two said outer layers, said multi-layered web
comprising:
a) paper making fibers;
b) from about 0.01% to about 3.0% by weight of a biodegradable
quaternary ammonium compound, wherein said biodegradable quaternary
ammonium compound is selected from the group consisting of:
##STR4## wherein each R.sub.2 substituent is a C.sub.1 -C.sub.6
alkyl or hydroxyalkyl group, benzyl group or mixtures thereof; each
R.sub.3 substituent is a C.sub.11 -C.sub.21 hydrocarbyl group, or
substituted hydrocarbyl or mixtures thereof; Y is --O--C(O)-- or
--C (O)--O-- or --NH--C(O)-- or --C(O)--NH--, or mixtures thereof;
n is 1 to 4 and X.sup.- is a suitable anion, ##STR5## wherein each
R.sub.2 is a C.sub.1 -C.sub.6 alkyl or hydroxyalkyl group, benzyl
group, or mixtures thereof; each R.sub.3 is a C.sub.11 -C.sub.21
hydrocarbyl or substituted hydrocarbyl group or mixtures thereof; Y
is --O--C (O)-- or --C(O)--O-- or --NH--C(O) or --C(O)--NH-- or
mixtures thereof and X.sup.- is a suitable anion,
and mixtures thereof;
c) from about 0.01% to about 3.0% by weight of a water soluble,
biodegradable polyhydroxy compound; and
d) from about 0.01% to about 3.0% by weight of a binder
material,
wherein a majority of said biodegradable quaternary ammonium
compound, said polyhydroxy compound, and said binder is contained
in at least one of said outer layers.
2. The multi-layered tissue paper web of claim 1 wherein a majority
of said biodegradable quaternam ammonium compound, said polyhydroxy
compound, and said binder is contained in the two said outer
layers.
3. The multi-layered tissue paper web of claim 2 wherein said
biodegradable quaternary ammonium compound is diester di(touch
hardened)tallow dimethyl ammonium chloride, said polyhydroxy
compound is polyoxyethylene glycol having a weight average
molecular weight of from about 200 to about 600, and said binder
material is a starch-based temporary wet strength resin.
4. The multi-layered tissue paper web of claim 1 wherein said inner
layer comprises relatively long paper making fibers having an
average length of at least about 2.0 mm and wherein each of two
said outer layers comprises relatively short paper making fibers
having an average length between about 0.2 and about 1.5 mm.
5. The multi-layered tissue paper web of claim 4 wherein said inner
layer comprises softwood fibers and each of two said outer layers
comprises hardwood fibers.
6. The multi-layered tissue paper web of claim 5 wherein said
softwood fibers are northern softwood Kraft fibers and wherein said
hardwood fibers are eucalyptus fibers.
7. The multi-layered tissue paper web of claim 4 wherein said inner
layer comprises softwood fibers or mixtures of softwood fibers and
low cost fibers, and at least one of said outer layers comprises
low cost fibers or mixtures of hardwood fibers and low cost
fibers.
8. The multi-layered tissue paper web of claim 7 wherein said low
cost fibers are selected from the group consisting of sulfite
fibers, thermomechanical pulp fibers, chemi-thermomechanical pulp
fibers, recycled fibers, and mixtures thereof.
9. The multi-layered tissue paper web of claim 1 wherein said web
comprises a single ply having three layers.
10. The multi-layered tissue paper web of claim 1 wherein said
binder material is selected from the group consisting of permanent
wet strength resins, temporary wet strength resins, dry strength
resins, retention aid resins and mixtures thereof.
11. The multi-layered tissue paper web of claim 10 wherein said
binder material is a permanent wet strength resin selected from the
group consisting of polyamide-epichlorohydrin resins,
polyacrylamide resins, and mixtures thereof.
12. The multi-layered tissue paper web of claim 10 wherein said
binder material is a starch-based temporary wet strength resin.
13. The multi-layered tissue paper web of claim 1 wherein said
biodegradable quaternary ammonium compound is: ##STR6## and R.sub.2
is methyl and R.sub.3 is C.sub.15 -C.sub.17 alkyl or alkenyl.
14. The multi-layered tissue paper web of claim 1 wherein Y is
--O--C(O)-- or --C(O)--O--.
15. The multi-layered tissue paper web of claim 1 wherein X.sup.--
is chloride or methyl sulfate.
16. The multi-layered tissue paper web of claim 1 wherein said
biodegradable quaternary ammonium compound is: ##STR7## and each
R.sub.2 is methyl, R.sub.3 is C.sub.15 -C.sub.17 alkyl or
alkenyl.
17. The multi-layered tissue paper web of claim 1 wherein said
polyhydroxy compound is selected from the group consisting of
glycerol, sorbitols, polyglycerols having a weight average
molecular weight from about 150 to about 800, polyoxyethylene
glycols and polyoxypropylene glycols having a weight average
molecular weight from about 200 to about 4000, and mixtures
thereof.
18. The multi-layered tissue paper web of claim 17 wherein said
polyhydroxy compound is selected from the group consisting of
polyoxyethylene glycols and polyoxypropylene glycols having a
weight average molecular weight from about 200 to about 1000.
19. The multi-layered tissue paper web of claim 17 wherein said
polyhydroxy compound is glycerol.
20. The multi-layered tissue paper web of claim 1 wherein the
weight ratio of the biodegradable quaternary ammonium compound to
the polyhydroxy compound ranges from about 1.0:0.3 to about
0.3:1.0.
21. The multi-layered tissue paper web of claim 20 wherein the
weight ratio of the biodegradable quaternary ammonium compound to
the polyhydroxy compound ranges from about 1.0:0.7 to about
0.7:1.0.
22. The multi-layered tissue paper web of claim 1 wherein said
tissue paper web is a toilet tissue.
23. The multi-layered tissue paper web of claim 1 wherein said
tissue paper web is a facial tissue.
24. A multi-layered tissue paper web comprising three superposed
layers, an inner layer and two outer layers, said inner layer being
located between two said outer layers, said multi-layered web
comprising:
a) paper making fibers;
b) from about 0.01% to about 3.0% by weight of a biodegradable
quaternary ammonium compound, said quaternary ammonium compound
comprising:
wherein
each Y is --O--(O)C--, or --C(O)--O--, or --NH--C(O)--, or
--C(O)--NH--;
m is 2 or 3;
n is 0 to 4;
p is 0 to 1;
q is 0 to 4;
q.gtoreq.p;
each R is a C.sub.1 -C.sub.6 alkyl group, hydroxyalkyl group,
benzyl group, or mixtures thereof;
each R.sub.2 is a C.sub.13 -C.sub.23 hydrocarbyl or substituted
hydrocarbyl substituent and X.sup.- is a suitable anion,
c) from about 0.01% to about 3.0% by weight of a water soluble,
biodegradable polyhydroxy compound; and
d) from about 0.01% to about 3.0% by weight of a binder
material,
wherein a majority of said biodegradable quaternary ammonium
compound, said polyhydroxy compound, and said binder is contained
in at least one of said outer layers.
25. The paper product according to claim 24 wherein m=2, n=2, p=0,
and q=0.
26. The paper product according to claim 24 wherein m=2, n=2, p=1,
and q=2.
Description
FIELD OF THE INVENTION
This invention relates to multi-layered tissue paper web. More
particularly, it relates to multi-layered tissue paper web
comprising biodegradable chemical softener compositions and binder
materials. The treated tissue webs can be used to make soft,
absorbent and lint resistance paper products such as facial tissue,
and toilet tissue products.
BACKGROUND OF THE INVENTION
Paper webs or sheets, sometimes called tissue or paper tissue webs
or sheets, find extensive use in modern society. Such items as
facial and toilet tissues are staple items of commerce. It has long
been recognized that four important physical attributes of these
products are their strength, their softness, their absorbency,
particularly their absorbency for aqueous systems; and their lint
resistance, particularly their lint resistance when wet. Research
and development efforts have been directed to the improvement of
each of these attributes without seriously affecting the others as
well as to the improvement of two or three attributes
simultaneously.
Strength is the ability of the product, and its constituent webs,
to maintain physical integrity and to resist tearing, bursting, and
shredding under use conditions, particularly when wet.
Softness is the tactile sensation perceived by the consumer as
he/she holds a particular product, rubs it across his/her skin, or
crumples it within his/her hand. This tactile sensation is provided
by a combination of several physical properties. One of the most
important physical properties related to softness is generally
considered by those skilled in the art to be the stiffness of the
paper web from which the product is made. Stiffness, in turn, is
usually considered to be directly dependent on the dry tensile
strength of the web and the stiffness of the fibers which make up
the web.
Absorbency is the measure of the ability of a product, and its
constituent webs, to absorb quantities of liquid, particularly
aqueous solutions or dispersions. Overall absorbency as perceived
by the consumer is generally considered to be a combination of the
total quantity of liquid a given mass of multi-layered tissue paper
will absorb at saturation as well as the rate at which the mass
absorbs the liquid.
Lint resistance is the ability of the fibrous product, and its
constituent webs, to bind together under use conditions,
particularly when wet. In other words, the higher the lint
resistance is, the lower the propensity of the web to lint will
be.
The use of wet strength resins to enhance the strength of a paper
web is widely known. For example, Westfelt described a number of
such materials and discussed their chemistry in Cellulose Chemistry
and Technology, Volume 13, at pages 813-825 (1979). Freimark et al.
in U.S. Pat. No. 3,755,220 issued Aug. 28, 1973 mention that
certain chemical additives known as debonding agents interfere with
the natural fiber-to-fiber bonding that occurs during sheet
formation in paper making processes. This reduction in bonding
leads to a softer, or less harsh, sheet of paper. Freimark et al.
go on to teach the use of wet strength resins in conjunction with
the use of debonding agents to off-set the undesirable effects of
the debonding agents. These debonding agents do reduce both dry
tensile strength and wet tensile strength.
Shaw, in U.S. Pat. No. 3,821,068, issued Jun. 28, 1974, also
teaches that chemical debonders can be used to reduce the
stiffness, and thus enhance the softness, of a tissue paper
web.
Chemical debonding agents have been disclosed in various references
such as U.S. Pat. No. 3,554,862, issued to Hervey et al. on Jan.
12, 1971. These materials include quaternary ammonium salts such as
cocotrimethylammonium chloride, oleyltrimethylammonium chloride,
di(hydrogenated)tallow dimethyl ammonium chloride and
stearyltrimethyl ammonium chloride.
Emanuelsson et al., in U.S. Pat. No. 4,144,122, issued Mar. 13,
1979, teach the use of complex quaternary ammonium compounds such
as bis(alkoxy(2-hydroxy)propylene) quaternary ammonium chlorides to
soften webs. These authors also attempt to overcome any decrease in
absorbency caused by the debonders through the use of nonionic
surfactants such as ethylene oxide and propylene oxide adducts of
fatty alcohols.
Armak Company, of Chicago, Ill., in their bulletin 76-17 (1977)
disclose the use of dimethyl di(hydrogenated)tallow ammonium
chloride in combination with fatty acid esters of polyoxyethylene
glycols to impart both softness and absorbency to tissue paper
webs.
One exemplary result of research directed toward improved paper
webs is described in U.S. Pat. No. 3,301,746, issued to Sanford and
Sisson on Jan. 31, 1967. Despite the high quality of paper webs
made by the process described in this patent, and despite the
commercial success of products formed from these webs, research
efforts directed to finding improved products have continued.
For example, Becker et al. in U.S. Pat. No. 4,158,594, issued Jan.
19, 1979, describe a method they contend will form a strong, soft,
fibrous sheet. More specifically, they teach that the strength of a
tissue paper web (which may have been softened by the addition of
chemical debonding agents) can be enhanced by adhering, during
processing, one surface of the web to a creping surface in a fine
patterned arrangement by a bonding material (such as an acrylic
latex rubber emulsion, a water soluble resin, or an elastomeric
bonding material) which has been adhered to one surface of the web
and to the creping surface in the fine patterned arrangement, and
creping the web from the creping surface to form a sheet
material.
Conventional quaternary ammonium compounds such as the well known
dialkyl dimethyl ammonium salts (e.g. ditallow dimethyl ammonium
chloride, ditallow dimethyl ammonium methyl sulfate,
di(hydrogenated)tallow dimethyl ammonium chloride etc . . . ) are
effective chemical debonding agents. However, these quaternary
ammonium compounds are hydrophobic and not biodegradable, and can
adversely affect the absorbency of the treated paper webs.
Applicants have discovered that mixing the biodegradable quaternary
ammonium compound with a polyhydroxy compound (e.g., glycerol,
sorbitols, polyglycerols or polyoxyethylene glycols) will enhance
both softness and absorbency rate of fibrous cellulose
materials.
Unfortunately the use of biodegradable chemical softening
compositions comprising a biodegradable quaternary ammonium
compound and a polyhydroxy compound can decrease the lint
resistance of the treated paper webs. Applicants have discovered
that the lint resistance can be improved through the use of
suitable binder materials such as wet and dry strength resins and
retention aid resins known in the paper making art.
The present invention is applicable to tissue paper in general, but
particularly applicable to multi-layered tissue paper products such
as those described in U.S. Pat. No. 3,994,771, issued to Morgan Jr.
et al. on Nov. 30, 1976, and incorporated herein by reference.
It is an object of this invention to provide soft, absorbent and
lint resistance multi-layered tissue paper products.
It is also a further object of this invention to provide a process
for making soft, absorbent, lint resistance multi-layered tissue
paper products.
These and other objects are obtained using the present invention,
as will become readily apparent from a reading of the following
disclosure.
SUMMARY OF THE INVENTION
The present invention provides soft, absorbent, lint resistant
multi-layered tissue paper products comprising paper making fibers,
biodegradable chemical softening compositions and binder materials.
Briefly, the biodegradable chemical softening composition comprises
a mixture of:
(a) from about 0.01% to about 3.0% of a biodegradable quaternary
ammonium compound; and
(b) from about 0.01% to about 3.0% of a polyhydroxy compound;
preferably selected from the group consisting of glycerol,
sorbitols, polyglycerols having a weight average molecular weight
of from about 150 to about 800 and polyoxyethylene glycols and
polyoxypropylene glycols having a weight average molecular weight
from about 200 to 4000.
The multi-layered paper web tissue comprises three superposed
layers, an inner layer and two outer layers, said inner layer being
located between two said outer layers. Preferably more than about
60% of the biodegradable quaternary ammonium compound and the
polyhydroxy compound is contained in at least one of said outer
layers, more preferably more than about 75% of the biodegradable
quaternary ammonium compound and most preferably more than about
90% of the biodegradable quaternary ammonium compound and the
polyhydroxy compound is contained in at least one of said outer
layers. Preferably more than about 60% of the binder is contained
in at least one of said outer layers, more preferably more than
about 75% of the binder is contained in at least one of said outer
layers, most preferably greater than about 90% of the binder is
contained in at least one of said outer layers.
Examples of preferred ester-functional quaternary ammonium
compounds suitable for use in the present invention include
compounds having the formulas: ##STR1## wherein each R.sub.2
substituent is a C.sub.1 -C.sub.6 alkyl or hydroxyalkyl group,
benzyl group or mixtures thereof; each R.sub.1 substituent is a
C.sub.12 -C.sub.22 hydrocarbyl group, or substituted hydrocarbyl
group or mixtures thereof; each R.sub.3 substituent is a C.sub.11
-C.sub.21 hydrocarbyl group, or substituted hydrocarbyl or mixtures
thereof.
These compounds can be considered to be mono or diester variations
of the well-known dialkyldimethylammonium salts such as diester
ditallow dimethyl ammonium chloride, diester distearyl dimethyl
ammonium chloride, monoester ditallow dimethyl ammonium chloride,
diester di(hydrogenated)tallow dimethyl ammonium methylsulfate,
diester di(hydrogenated)tallow dimethyl ammonium chloride,
monoester di(hydrogenated)tallow dimethyl ammonium chloride, and
mixtures thereof, with the diester variations of di(non
hydrogenated)tallow dimethyl ammonium chloride, Di(Touch
Hydrogenated)Tallow DiMethyl Ammonium Chloride (DEDTHTDMAC) and
Di(Hydrogenated)Tallow DiMethyl Ammonium Chloride (DEDHTDMAC), and
mixtures thereof being preferred. Depending upon the product
characteristic requirements, the saturation level of the ditallow
can be tailored from non hydrogenated (soft) to touch, partially or
completely hydrogenated (hard).
Without being bound by theory, it is believed that the ester
moiety(ies) lends biodegradability to these compounds. Importantly,
the ester-functional quaternary ammonium compounds used herein
biodegrade more rapidly than do conventional dialkyl dimethyl
ammonium chemical softeners.
Examples of polyhydroxy compounds useful in the present invention
include glycerol, sorbitols, polyglycerols having a weight average
molecular weight of from about 150 to about 800 and polyoxyethylene
glycols having a weight average molecular weight of from about 200
to about 4000, with polyoxyethylene glycols having a weight average
molecular weight of from about 200 to about 600 being
preferred.
The term binder refers to the various wet and dry strength
additives, and retention aids known in the art. These materials
improve the lint resistance of the tissue paper webs of the present
invention as well as counteracting any decrease in tensile strength
caused by biodegradable chemical softening compositions. Examples
of suitable binder materials include permanent wet strength resins
(i.e. Kymene.RTM. 557H marketed by Hercules Incorporated of
Wilmington, Del.), temporary wet strength resins (i.e. National
starch 78-0080 marketed by National Starch and Chemical corporation
of New-York, N.Y.), dry strength resins (i.e. Acco.RTM. 514,
Acco.RTM. 711 marketed by American Cyanamid company of Wayne, N.J.)
and retention aid resins (i.e. Percol.RTM. 175 marketed by Allied
Colloids of Sulfolk, Vir.).
Briefly, the process for making the multi-layered tissue paper webs
of the present invention comprises the steps of formation of a
multi-layered paper making furnish from the aforementioned
components, deposition of the multi-layered paper making furnish
onto a foraminous surface such as a Fourdrinier wire, and removal
of the water from the deposited furnish.
All percentages, ratios and proportions herein are by weight unless
otherwise specified.
BRIEF DESCRIPTION OF THE DRAWINGS
While the Specification concludes with claims particularly pointing
out and distinctly claiming the present invention, it is believed
the invention is better understood from the following description
taken in conjunction with the associated drawings, in which:
FIG. 1 is a schematic cross-sectional view of a three-layered
single ply toilet tissue in accordance with the present
invention.
FIG. 2 is a schematic cross-sectional view of a two-layered two-ply
facial tissue in accordance with the present invention.
The present invention is described in more detail below.
DETAILED DESCRIPTION OF THE INVENTION
While this specification concludes with claims particularly
pointing out and distinctly claiming the subject matter regarded as
the invention, it is believed that the invention can be better
understood from a reading of the following detailed description and
of the appended examples.
As used herein, the term "lint resistance" is the ability of the
fibrous product, and its constituent webs, to bind together under
use conditions, particularly when wet. In other words, the higher
the lint resistance is, the lower the propensity of the web to lint
will be.
As used herein, the term "binder" refers to the various wet and dry
strength resins and retention aid resins known in the paper making
art.
As used herein, the term "water soluble" refers to materials that
are soluble in water to at least 3% at 25.degree. C.
As used herein, the terms "tissue paper web, paper web, web, paper
sheet and paper product" all refer to sheets of paper made by a
process comprising the steps of forming an aqueous papermaking
furnish, depositing this furnish on a foraminous surface, such as a
Fourdrinier wire, and removing the water from the furnish as by
gravity or vacuum-assisted drainage, with or without pressing, and
by evaporation.
As used herein, an "aqueous paper making furnish" is an aqueous
slurry of paper making fibers and the chemicals described
hereinafter.
As used herein, the term "multi-layered tissue paper web,
multi-layered paper web, multi-layered web, multi-layered paper
sheet and multi-layered paper product" all refer to sheets of paper
prepared from two or more layers of aqueous paper making furnish
which are preferably comprised of different fiber types, the fibers
typically being relatively long softwood and relatively short
hardwood fibers as used in tissue paper making. The layers are
preferably formed from the deposition of separate streams of dilute
fiber slurries upon one or more endless foraminous screens. If the
individual layers are initially formed on separate wires, the
layers are subsequently combined when wet to form a layered
composite web.
The first step in the process of this invention is the forming of
an aqueous paper making furnish. The furnish comprises paper making
fibers (hereinafter sometimes referred to as wood pulp), and a
mixture of at least one biodegradable quaternary ammonium compound,
a polyhydroxy compound and binder materials all of which will be
hereinafter described.
It is anticipated that wood pulp in all its varieties will normally
comprise the paper making fibers used in this invention. However,
other cellulose fibrous pulps, such as cotton liners, bagasse,
rayon, etc., can be used and none are disclaimed. Wood pulps useful
herein include chemical pulps such as Kraft, sulfite and sulfate
pulps as well as mechanical pulps including for example, ground
wood, thermomechanical pulps and ChemiThermoMechanical Pulp (CTMP).
Pulps derived from both deciduous and coniferous trees can be
used.
Both hardwood pulps and softwood pulps as well as blends of the two
may be employed. The terms hardwood pulps as used herein refers to
fibrous pulp derived from the woody substance of deciduous trees
(angiosperms): wherein softwood pulps are fibrous pulps derived
from the woody substance of coniferous trees (gymnosperms).
Hardwood pulps such as eucalyptus are particularly suitable for the
outer layers of the multi-layered tissue webs described
hereinafter, whereas northern softwood Kraft pulps are preferred
for the inner layer(s) or ply(s). Also applicable to the present
invention are fibers derived from recycled paper, which may contain
any or all of the above categories as well as other non-fibrous
materials such as fillers and adhesives used to facilitate the
original paper making.
Biodegradable chemical softener compositions
The present invention contains as an essential component a mixture
of a biodegradable quaternary ammonium compound and a polyhydroxy
compound. The ratio of the biodegradable quaternary ammonium
compound to the polyhydroxy compound ranges from about 1.0:0.1 to
0.1:1.0; preferably, the weight ratio of the biodegradable
quaternary ammonium compound to the polyhydroxy compound is about
1.0:0.3 to 0.3:1.0; more preferably, the weight ratio of the
biodegradable quaternary ammonium compound to the polyhydroxy
compound is about 1.0:0.7 to 0.7:1.0, although this ratio will vary
depending upon the molecular weight of the particular polyhydroxy
compound and/or biodegradable quaternary ammonium compound
used.
Each of these types of compounds will be described in detail
below.
A. Biodegradable quaternary ammonium compound
The biodegradable chemical softening composition contains as an
essential component from about 0.01% to about 3.00% by weight,
preferably from about 0.01% to about 1.00% by weight of a
biodegradable quaternary ammonium compound, preferably
biodegradable quaternary ammonium compounds having the formula:
wherein
each Y is --O--(O)C--, or --C(O)--O--, or --NH--C(O)--, or
--C(O)--NH--;
m is 1 to 3;
n is 0 to 4;
p is 0 to 1;
q is 0 to 4;
q.gtoreq.p;
each R is a C.sub.1 -C.sub.6 alkyl group, hydroxyalkyl group,
benzyl group, or mixtures thereof;
each R.sub.2 is a C.sub.13 -C.sub.23 hydrocarbyl or substituted
hydrocarbyl substituent; and
X.sup.- is any softener-compatible anion.
Specific examples of biodegradable quaternary ammonium compounds
having the formulas: ##STR2## wherein each R.sub.2 substituent is a
C.sub.1 -C.sub.6 alkyl or hydroxyalkyl group, benzyl group or
mixtures thereof, each R.sub.1 substituent is a C.sub.12 -C.sub.22
hydrocarbyl group, or substituted hydrocarbyl group or mixtures
thereof, each R.sub.3 substituent is a C.sub.11 -C.sub.21
hydrocarbyl group, or substituted hydrocarbyl or mixtures thereof,
Y is --O--C(O)-- or --C(O)--O-- or --NH--C(O) or --C(O)--NH-- or
mixtures thereof, n is 1 to 4 and X.sup.- is a suitable anion, for
example, chloride, bromide, methylsulfate, ethyl sulfate, nitrate
and the like.
As discussed in Swern, Ed. in Bailey's Industrial Oil and Fat
Products, Third Edition, John Wiley and Sons (New York 1964),
tallow is a naturally occurring material having a variable
composition. Table 6.13 in the above-identified reference edited by
Swern indicates that typically 78% or more of the fatty acids of
tallow contain 16 or 18 carbon atoms. Typically, half of the fatty
acids present in tallow are unsaturated, primarily in the form of
oleic acid. Synthetic as well as natural "tallows" fall within the
scope of the present invention. It is also known that depending
upon the product characteristic requirements, the saturation level
of the ditallow can be tailored from non hydrogenated (soft) to
touch, partially or completely hydrogenated (hard). All of
above-described levels of saturations are expressly meant to be
included within the scope of the present invention.
It will be understood that substituents R.sub.1, R.sub.2 and
R.sub.3 may optionally be substituted with various groups such as
alkoxyl, hydroxyl, or can be branched, but such materials are not
preferred herein. Preferably, each R.sub.1 is C.sub.12 -C.sub.18
alkyl and/or alkenyl, most preferably each R.sub.1 is
straight-chain C.sub.16 -C.sub.18 alkyl and/or alkenyl. Preferably,
each R.sub.2 is methyl or hydroxyethyl. Preferably R.sub.3 is
C.sub.13 -C.sub.17 alkyl and/or alkenyl, most preferably R.sub.3 is
straight chain C.sub.15 -C.sub.17 alkyl and/or alkenyl, and X.sup.-
is chloride or methyl sulfate. Furthermore the ester-functional
quaternary ammonium compounds can optionally contain up to about
10% of the mono(long chain alkyl) derivatives, e.g.,
(R.sub.2).sub.2 --N.sup.+ --((CH.sub.2).sub.2 OH) ((CH.sub.2).sub.2
OC(O)R.sub.3) X.sup.- as minor ingredients. These minor ingredients
can act as emulsifiers and are useful in the present invention.
Specific examples of ester-functional quaternary ammonium compounds
having the structures named above and suitable for use in the
present invention include the well-known diester dialkyl dimethyl
ammonium salts such as diester ditallow dimethyl ammonium chloride,
monoester ditallow dimethyl ammonium chloride, diester ditallow
dimethyl ammonium methyl sulfate, diester di(hydrogenated)tallow
dimethyl ammonium methyl sulfate, diester di(hydrogenated)tallow
dimethyl ammonium chloride, and mixtures thereof. Diester ditallow
dimethyl ammonium chloride and diester di(hydrogenated)tallow
dimethyl ammonium chloride are particularly preferred. These
particular materials are available commercially from Sherex
Chemical Company Inc. of Dublin, Ohio under the tradename "ADOGEN
DDMC.RTM.".
Di-quat variations of the ester-functional quaternary ammonium
compound can also be used, and are meant to fall within the scope
of the present invention. These compounds have the formula:
##STR3##
In the structure named above each R.sub.2 is a C.sub.1 -C.sub.6
alkyl or hydroxyalkyl group, R.sub.3 is C.sub.11 -C.sub.21
hydrocarbyl group, n is 2 to 4 and X.sup.- is a suitable anion,
such as an halide (e.g., chloride or bromide) or methyl sulfate.
Preferably, each R.sub.3 is C.sub.13 -C.sub.17 alkyl and/or
alkenyl, most preferably each R.sub.3 is straight-chain C.sub.15
-C.sub.17 alkyl and/or alkenyl, and R.sub.2 is a methyl.
B. Polyhydroxy Compound
The biodegradable chemical softening composition contains as an
essential component from about 0.01% to about 3.00% by weight,
preferably from about 0.01% to about 1.00% by weight of a
polyhydroxy compound.
Examples of polyhydroxy compounds useful in the present invention
include glycerol, sorbitols, polyglycerols having a weight average
molecular weight of from about 150 to about 800 and polyoxyethylene
glycols and polyoxypropylene glycols having a weight average
molecular weight of from about 200 to about 4000, preferably from
about 200 to about 1000, most preferably from about 200 to about
600. Polyoxyethylene glycols having an weight average molecular
weight of from about 200 to about 600 are especially preferred.
Mixtures of the above-described polyhydroxy compounds may also be
used. For example, mixtures of glycerol and polyoxyethylene glycols
having a weight average molecular weight from about 200 to 1000,
more preferably from about 200 to 600 are useful in the present
invention. Preferably, the weight ratio of glycerol to
polyoxyethylene glycol ranges from about 10:1 to 1:10.
A particularly preferred polyhydroxy compound is polyoxyethylene
glycol having an weight average molecular weight of about 400. This
material is available commercially from the Union Carbide Company
of Danbury, Conn. under the tradename "PEG-400".
The biodegradable chemical softening composition described above
i.e. mixture of a biodegradable quaternary ammonium compounds and a
polyhydroxy compound are preferably diluted to a desired
concentration to form a dispersion of the quat and polyhydroxy
compounds before being added to the aqueous slurry of paper making
fibers, or furnish, in the wet end of the paper making machine at
some suitable point ahead of the Fourdrinier wire or sheet forming
stage. However, applications of the above described biodegradable
chemical softening composition subsequent to formation of a wet
tissue web and prior to drying of the web to completion will also
provide significant softness, absorbency, and wet strength benefits
and are expressly included within the scope of the present
invention.
It has been discovered that the biodegradable chemical softening
composition is more effective when the biodegradable quaternary
ammonium compound and the polyhydroxy compound are first pre-mixed
together before being added to the paper making furnish. A
preferred method, as will be described in greater detail
hereinafter in Example 1, consists of first heating the polyhydroxy
compound to a temperature of about 66.degree. C. (150.degree. F.),
and then adding the biodegradable quaternary ammonium compound to
the hot polyhydroxy compound to form a homogenous fluid. The weight
ratio of the quaternary ammonium compound to the polyhydroxy
compound ranges from about 1.0:0.1 to 0.1:1.0; preferably, the
weight ratio of the biodegradable quaternary ammonium compound to
the polyhydroxy compound is about 1.0:0.3 to 0.3:1.0; more
preferably, the weight ratio of the biodegradable quaternary
ammonium compound to the polyhydroxy compound is about 1.0:0.7 to
0.7:1.0, although this ratio will vary depending upon the molecular
weight of the polyhydroxy compound and/or biodegradable quaternary
ammonium compound used.
It has unexpectedly been found that the adsorption of the
polyhydroxy compound onto paper is significantly enhanced when it
is premixed with the biodegradable quaternary ammonium compound and
added to the paper by the above described process. In fact, at
least 20% of the polyhydroxy compound and the biodegradable
quaternary ammonium compound added to the fibrous cellulose are
retained; preferably, the retention level of biodegradable
quaternary ammonium compound and the polyhydroxy compound is from
about 50% to about 90% of the added levels.
Importantly, adsorption occurs at a concentration and within a time
frame that are practical for use during paper making. In an effort
to better understand the surprisingly high retention rate of
polyhydroxy compound onto the paper, the physical science of the
melted solution and the aqueous dispersion of a DiEster Di(Touch
Hardened)Tallow DiMethyl Ammonium Chloride (DEDTHTDMAC), and
polyoxyethylene glycol 400 were studied.
Without wishing to be bound by theory, or to otherwise limit the
present invention, the following discussion is offered for
explaining how the ester-functional quaternary ammonium compound
promotes the adsorption of the polyhydroxy compound onto paper.
DEDTHTDMAC (DiEster Di(Touch Hardened)Tallow DiMethyl Ammonium
Chloride) exist as a mixture of liquid crystalline and crystalline
phases, at equilibrium. X-ray data indicate that commercial
DEDTHTDMAC is, in fact, a liquid crystalline phase showing no
evidence of crystalline states.
Mixtures of DEDTHTDMAC with PEG-400
Phase studies of these two materials using the step-wise dilution
method demonstrate that their physical behavior is similar to that
of di(hydrogenated)tallow dimethyl ammonium chloride. These
compounds are miscible over a wide range of temperatures
(.gtoreq.50.degree. C.), which indicates that dispersions may be
prepared from these mixtures over a comparable range of
temperatures. No upper temperature limit of miscibility exists. The
X-ray data show that a mixture of crystal and liquid phases do, in
fact, exist in DEDTHTDMAC/PEG-400 mixtures.
Mixtures of DEDTHTDMAC with glycerol
A 1:1 weight ratio mixture of DEDTHTDMAC and glycerol appears (from
direct observation and X-ray data) to be a liquid phase. While
glycerol is capable of forming liquid crystal phases in combination
with other surfactants, it appears not to do so in this system at
this composition.
Mixtures of DEDHTDMAC with PEG-400
Phase studies of these two materials using the step-wise dilution
method demonstrate that their physical behavior is similar to that
of DEDTHTDMAC. These compounds are miscible over a wide range of
temperatures (>67.degree. C.), which indicates that dispersions
may be prepared from these mixtures over a comparable range of
temperatures. No upper temperature limit of miscibility exists.
Physical state of mixtures of quats/polyhydroxy compounds/water
Dispersions of either of these materials may be prepared by
diluting a mixture, that is held at a temperature at which the
polyhydroxy compound and the ester-functional quaternary ammonium
salt are miscible, with water. Neither DEDTHTDMAC nor DEDHTDMAC are
soluble in water, so the dilution of either dry phase with water
will precipitate the ester-functional quaternary ammonium compound
as small particles. The polyhydroxy compound is soluble with water
in all proportions, so it is not precipitated.
The addition of mixtures of about equal parts of DEDTHTDMAC and
polyhydroxy compounds (e.g. glycerol, PEG-400 etc. . . . ) to
water, so as to form a mixture containing about 1% of DEDTHTDMAC
will precipitate the DEDTHTDMAC. Most likely, the DEDTHTDMAC phase
near room temperature will be the lamellar liquid crystal.
Colloidal structure of dispersions
The liquid crystal phase in the diluted mixtures exists as vesicles
which, for the most part, are closed and spherical. The formation
of such dispersion likely results from the large osmotic pressure
gradients that momentarily exist during the process. The origin of
these pressure gradients is the spatial gradients in the
composition (and thermodynamic activity) of water that are created.
Since the liquid phase of DEDTHTDMAC/glycerol mixtures may exist
over a wide range of temperature, one may also produce dispersions
over a wide range of temperatures.
Cryoelectron microscopy demonstrates that the particles present are
about 0.1 to 1.0 micrometers in size, and highly varied in
structure. Some are sheets (curved or flat), while others are
closed vesicles. The membranes of all these particles are bilayers
of molecular dimensions in which the head groups are exposed to
water, the tails are together. The PEG is presumed to be associated
with these particles. The application of dispersions prepared in
this manner to paper results in attachment of the ester-functional
quaternary ammonium ion to the paper, strongly promotes the
adsorption of the polyhydroxy compound onto paper, and produces the
desired modification of softness and retention of wettability.
State of the dispersions
When the above described dispersions are cooled, the partial
crystallization of the material within the colloidal particles may
occur. However, it is likely that the attainment of the equilibrium
state will require a long time (perhaps months), so that a
disordered particle whose membranes are either a liquid crystal or
a disordered crystal phase is interacting with the paper.
Preferably, the biodegradable chemical softening compositions
described herein are used before the equilibrium state has been
attained.
It is believed that the vesicles containing biodegradable quats and
polyhydroxy compounds (e.g. glycerol, PEG-400 etc. . . . ) break
apart upon drying of the fibrous cellulosic material. Once the
vesicle is broken, the majority of the PEG component may penetrate
into the interior of the cellulose fibers where it enhances the
fiber flexibility. Importantly, some of the PEG is retained on the
surface of the fiber where it acts to enhance the absorbency rate
of the cellulose fibers. Due to ionic interaction, the cationic
portion of the biodegradable quats component stays on the surface
of the cellulose fiber, where it enhances the surface feel and
softness of the paper product.
Binder materials
The present invention contains as an essential component from about
0.01% to about 3.0%, preferably from about 0.01% to about 1% by
weight of a binder material selected from the group consisting of
permanent wet strength resins, temporary wet strength resins, dry
strength resins, retention aid resins and mixtures thereof. The
binder materials act to control linting and also to offset the loss
in tensile strength, if any, resulting from the biodegradable
chemical softener compositions.
If permanent wet strength is desired, the binder materials can be
chosen from the following group of chemicals:
polyamide-epichlorohydrin, polyacrylamides, styrene-butadiene
latexes; insolubilized polyvinyl alcohol; urea-formaldehyde;
polyethyleneimine; chitosan polymers and mixtures thereof.
Polyamide-epichlorohydrin resins are cationic wet strength resins
which have been found to be of particular utility. Suitable types
of such resins are described in U.S. Pat. No. 3,700,623, issued on
Oct. 24, 1972, and 3,772,076, issued on Nov. 13, 1973, both issued
to Keim and both being hereby incorporated by reference. One
commercial source of a useful polyamide-epichlorohydrin resins is
Hercules, Inc. of Wilmington, Del., which markets such resin under
the mark Kymeme.RTM. 557H.
Polyacrylamide resins have also been found to be of utility as wet
strength resins or retention aids. These resins are described in
U.S. Pat. Nos. 3,556,932, issued on Jan. 19, 1971, to Coscia, et
al. and 3,556,933, issued on Jan. 19, 1971, to Williams et al.,
both patents being incorporated herein by reference. One commercial
source of polyacrylamide resins is American Cyanamid Co. of
Stanford, Conn., which markets one such resin under the mark
Parez.RTM. 631 NC. Other commercial sources of cationic
polyacrylamide resins are Allied Colloids of Sulfolk, Va., and
Hercules, Inc. of Wilmington, Del., which markets such resins under
the marks Percol.RTM. 175 and Reten.RTM. 1232.
Still other water-soluble cationic resins finding utility in this
invention are urea formaldehyde and melamine formaldehyde resins.
The more common functional groups of these polyfunctional resins
are nitrogen containing groups such as amino groups and methylol
groups attached to nitrogen. Polyethylenimine type resins may also
find utility in the present invention.
If temporary wet strength is desired, the binder materials can be
chosen from the following group of starch-based temporary wet
strength resins: cationic dialdehyde starch-based resin (such as
Caldas produced by Japan Carlet or Cobond 1000 produced by National
Starch); dialdehyde starch; and/or the resin described in U.S. Pat.
No. 4,981,557 issued on Jan. 1, 1991, to Bjorkquist and
incorporated herein by reference.
If dry strength is desired, the binder materials can be chosen from
the following group of materials: polyacrylamide (such as
combinations of Cypro 514 and Accostrength 711 produced by American
cyanamid of Wayne, N.J.); starch (such as corn starch or potato
starch); polyvinyl alcohol (such as Airvol 540 produced by Air
Products Inc of Allentown, Pa.); guar or locust bean gums;
polyacrylate latexes; and/or carboxymethyl cellulose (such as
Aqualon CMC-T from Aqualon Co., Wilmington, Del.). In general,
suitable starch for practicing the present Invention is
characterized by water solubility, and hydrophilicity. Exemplary
starch materials include corn starch and potato starch, albeit it
is not intended to thereby limit the scope of suitable starch
materials; and waxy corn starch that is known industrially as
amioca starch is particularly preferred. Amioca starch differs from
common corn starch in that it is entirely amylopectin, whereas
common corn starch contains both amplopectin and amylose. Various
unique characteristics of amioca starch are further described in
"Amioca--The Starch from Waxy Corn", H. H. Schopmeyer, Food
Industries, December 1945, pp. 106-108 (Vol. pp. 1476-1478). The
starch can be in granular or dispersed form albeit granular form is
preferred. The starch is preferably sufficiently cooked to induce
swelling of the granules. More preferably, the starch granules are
swollen, as by cooking, to a point just prior to dispersion of the
starch granule. Such highly swollen starch granules shall be
referred to as being "fully cooked". The conditions for dispersion
in general can vary depending upon the size of the starch granules,
the degree of crystallinity of the granules, and the amount of
amylose present. Fully cooked amioca starch, for example, can be
prepared by heating an aqueous slurry of about 4.times. consistency
of starch granules at about 190.degree. F. (about 88.degree. C.)
for between about 30 and about 40 minutes. Other exemplary starch
materials which may be used include modified cationic starches such
as those modified to have nitrogen containing groups such as amino
groups and methylol groups attached to nitrogen, available from
National Starch and Chemical Company, (Bridgewater, N.J.). Such
modified starch materials are used primarily as a pulp furnish
additive to increase wet and/or dry strength. Considering that such
modified starch materials are more expensive than unmodified
starches, the latter have generally been preferred.
Methods of application include, the same previously described with
reference to application of other chemical additives preferably by
wet end addition, spraying; and, less preferably, by printing. The
binder may be applied to the tissue paper web alone, simultaneously
with, prior to, or subsequent to the addition of softener,
absorbency, and/or aesthetic additives. At least an effective
amount of a binder, preferably starch, to provide lint control and
concomitant strength increase upon drying relative to a non-binder
treated but otherwise identical sheet is preferably applied to the
sheet. Preferably, between about 0.01% and about 3.0% of a binder
is retained in the dried sheet, calculated on a dry fiber weight
basis; and, more preferably, between about 0.1% and about 1.0% of a
binder material, preferably starch-based, is retained.
The second step in the process of this invention is the depositing
of the multi-layered paper making furnish using the above described
chemical softener composition and binder materials as additives on
a foraminous surface and the third step is the removing of the
water from the furnish so deposited. Techniques and equipment which
can be used to accomplish these two processing steps will be
readily apparent to those skilled in the paper making art.
Preferred multi-layered tissue paper embodiments of the present
invention contain from about 0.01% to about 3.0%, more preferably
from about 0.1% to 1.0% by weight, on a dry fiber basis of the
biodegradable chemical softening composition and binder materials
described herein.
The present invention is applicable to multi-layered tissue paper
in general, including but not limited to conventionally
felt-pressed multi-layered tissue paper; high bulk pattern
densified multi-layered tissue paper; and high bulk, uncompacted
multi-layered tissue paper. The multi-layered tissue paper products
made therefrom may be of a single-ply or multi-ply construction.
Tissue structures formed from layered paper webs are described in
U.S. Pat. No. 3,994,771, Morgan, Jr. et al. issued Nov. 30, 1976,
and incorporated herein by reference. In general, a wet-laid
composite, soft, bulky and absorbent paper structure is prepared
from two or more layers of furnish which are preferably comprised
of different fiber types. The layers are preferably formed from the
deposition of separate streams of dilute fiber slurries, the fibers
typically being relatively long softwood and relatively short
hardwood fibers as used in multi-layered tissue paper making, upon
one or more endless foraminous screens. If the individual layers
are initially formed on separate wires, the layers are subsequently
combined when wet to form a layered composite web. The layered web
is subsequently caused to conform to the surface of an open mesh
drying/imprinting fabric by the application of a fluid force to the
web and thereafter thermally predried on said fabric as part of a
low density paper making process. The layered web may be stratified
with respect to fiber type or the fiber content of the respective
layers may be essentially the same. The multi-layered tissue paper
preferably has a basis weight of between 10 g/m.sup.2 and about 65
g/m.sup.2, and density of about 0.60 g/cm.sup.3 or less.
Preferably, basis weight will be below about 35 g/m.sup.2 or less;
and density will be about 0.30 g/cm.sup.3 or less. Most preferably,
density will be between 0.04 g/cm.sup.3 and 0.20 g/cm.sup.3.
The multi-layered tissue paper webs of the present invention
comprise at least two superposed layers, a first layer and at least
one second layer contiguous with the first layer. Preferably, the
multi-layered tissue papers comprise three superposed layers, an
inner or center layer, and two outer layers, with the inner layer
located between the two outer layers. The two outer layers
preferably comprise a primary filamentary constituent of about 60%
or more by weight of relatively short paper making fibers having an
average fiber between about 0.2 and about 1.5 mm. These short paper
making fibers are typically hardwood fibers, preferably, eucalyptus
fibers. Alternatively, low cost sources of short fibers such as
sulfite fibers, thermomechanical pulp fibers,
chemi-thermomechanical pulp fibers, recycled fibers including
fibers fractionated from recycled fibers, and mixtures thereof can
be used in one or both of the outer layers or blended in the inner
layer, if desired. The inner layer preferably comprises a primary
filamentary constituent of about 60% or more by weight of
relatively long paper making fibers having an average fiber length
of least about 2.0 mm. These long paper making fibers are typically
softwood fibers, preferably, northern softwood Kraft fibers. FIG. 1
is a schematic cross-sectional view of a three-layered single ply
toilet tissue in accordance with the present invention. Referring
to FIG. 1, the three layered single ply web 10, comprises three
superposed layers, inner layer 12, and two outer layers 11. Outer
layers 11 are comprised primarily of short paper making fibers 16;
whereas inner layer 12 is comprised primarily of long paper making
fibers 17.
In an alternate preferred embodiment of the present invention,
multi-ply tissue paper products are formed by placing at least two
multi-layered tissue paper webs in juxtaposed relation. For
example, a two-ply tissue paper product can be made comprising a
first two-layered tissue paper web and a second two-layered tissue
paper web in juxtaposed relation. In this example, each ply is a
two-layer tissue sheet comprising a first layer and a second layer.
The first layer preferably comprises the short hardwood fibers and
the second layer preferably comprises the long softwood fibers. The
two plys are combined in a manner such that the short hardwood
fibers of each ply face outwardly, and the layers containing the
long softwood fibers face inwardly. FIG. 2 is a schematic
cross-sectional view of a two-layered two-ply facial tissue in
accordance with the present invention. Referring to FIG. 2, the
two-layered two-ply web 20, is comprised of two plies 15 in
juxtaposed relation. Each ply 15 is comprised of inner layer 19,
and outer layer 18. Outer layers 18 are comprised primarily of
short paper making fibers 16; whereas inner layers 19 are comprised
primarily of long paper making fibers 17. Similarly three-ply
tissue paper products can be made by placing three multi-layered
tissue paper webs in juxtaposed relation.
It should not be inferred from the above discussion that the
present invention is limited to tissue paper products comprising
three-layers--single ply or two-plys--two layers, etc. Tissue paper
products consisting of three or more plys in combination with each
ply consisting of one or more layers are also expressly meant to be
included within the scope of the present invention.
Preferably, the majority of the biodegradable quaternary ammonium
compound and the polyhydroxy compound is contained in at least one
of the outer layers of the multi-layered tissue paper web of the
present invention. More preferably, the majority of the
biodegradable quaternary ammonium compound and the polyhydroxy
compound is contained in both of the outer layers. The term
"majority" as used herein refers to more than one half of the total
amount, by weight, of the biodegradable quaternary ammonium
compound and the polyhydroxy compound. Preferably more than 60%,
more preferably more than about 75%, and most preferably more than
about 90% of the biodegradable quaternary ammonium compound and the
polyhydroxy compound is contained in at least one of said outer
layers, and more preferably in both of the outer layers. It has
been discovered that the biodegradable chemical softening
composition is most effective when added to the outer layers or
plies of the tissue paper products. There, the mixture of the
biodegradable quaternary compound and polyhdroxy compound act to
enhance both the softness and the absorbency of the multi-layered
tissue products of the present invention. Referring to FIGS. 1 and
2, the biodegradable chemical softening composition comprising a
mixture of the biodegradable quaternary ammonium compound and the
polyhdroxy compound is schematically represented by dark circles
14. It can be seen in FIGS. 1 and 2 that the majority of the
biodegradable chemical softening composition 14 is contained in
outer layers 11 and 18, respectively.
However, it has also been discovered that the lint resistance of
the multilayered tissue paper products decreases with the inclusion
of the biodegradable quaternary ammonium compound and the
polyhdroxy compound. Therefore, binder materials are used for
linting control and to increase the tensile strength. Preferably,
the majority of the binder is contained in at least one of the
outer layers of the multi-layered tissue paper web of the present
invention. More preferably, the majority of the binder is contained
in both of the outer layers. The term "majority" as used herein
refers to more than one half of the total amount of the binder.
Preferably more than about 60%, more preferably more than about
75%, and most preferably more than about 90% of the binder is
contained in at least one of said outer layers, and more preferably
in both of the outer layers. It has been discovered that the binder
is most effective when added to the outer layers or plies of the
tissue paper products. There, the binder acts to control the
linting of the multi-layered tissue products of the present
invention. Referring to FIGS. 1 and 2, the binder is schematically
represented by white circles 13. It can be seen in FIGS. 1 and 2
that the majority of the binder 13 is contained in outer layers 11
and 18, respectively.
The combination of the biodegradable chemical softening composition
comprising a biodegradable quaternary ammonium compound and a
polyhdroxy compound in conjunction with a binder material results
in a tissue paper product having superior softness, absorbency, and
lint resistance properties. Selectively adding the majority of the
biodegradable chemical softening composition to the outer layers or
plys of the tissue paper, enhances its effectiveness. As discussed
above, the majority of the binder materials are also preferably
disposed on the outer layers where they act to control linting.
Surprisingly, Applicants have discovered that the addition of
binders in combination with the biodegradable chemical softening
compositions to the outer layers results in a softer tissue paper
product than can be achieved through the addition of softeners
alone. This is completely unexpected, because the addition of
binder materials alone to the outer layers of tissue paper products
will have a detrimental effect on tissue softness.
Conventionally pressed multi-layered tissue paper and methods for
making such paper are known in the art. Such paper is typically
made by depositing paper making furnish on a foraminous forming
wire. This forming wire is often referred to in the art as a
Fourdrinier wire. Once the furnish is deposited on the forming
wire, it is referred to as a web. The web is dewatered by
transferring to a dewatering felt, pressing the web and drying at
elevated temperature. The particular techniques and typical
equipment for making webs according to the process just described
are well known to those skilled in the art. In a typical process, a
low consistency pulp furnish is provided in a pressurized headbox.
The headbox has an opening for delivering a thin deposit of pulp
furnish onto the Fourdrinier wire to form a wet web. The web is
then typically dewatered to a fiber consistency of between about 7%
and about 25% (total web weight basis) by vacuum dewatering and
further dewatered by pressing operations wherein the web is
subjected to pressure developed by opposing mechanical members, for
example, cylindrical rolls.
The dewatered web is then further pressed during transfer and being
dried by a stream drum apparatus known in the art as a Yankee
dryer. Pressure can be developed at the Yankee dryer by mechanical
means such as an opposing cylindrical drum pressing against the
web. Vacuum may also be applied to the web as it is pressed against
the Yankee surface. Multiple Yankee dryer drums may be employed,
whereby additional pressing is optionally incurred between the
drums. The multi-layered tissue paper structures which are formed
are referred to hereinafter as conventional, pressed, multi-layered
tissue paper structures. Such sheets are considered to be compacted
since the web is subjected to substantial mechanical compression
forces while the fibers are moist and are then dried while in a
compressed state.
Pattern densified multi-layered tissue paper is characterized by
having a relatively high bulk field of relatively low fiber density
and an array of densified zones of relatively high fiber density.
The high bulk field is alternatively characterized as a field of
pillow regions. The densified zones are alternatively referred to
as knuckle regions. The densified zones may be discretely spaced
within the high bulk field or may be interconnected, either fully
or partially, within the high bulk field. Preferred processes for
making pattern densified tissue webs are disclosed in U.S. Pat. No.
3,301,746, issued to Sanford and Sisson on Jan. 31, 1967, U.S. Pat.
No. 3,974,025, issued to Peter G. Ayers on Aug. 10, 1976, and U.S.
Pat. No. 4,191,609, issued to Paul D. Trokhan on Mar. 4, 1980, and
U.S. Pat. No. 4,637,859, issued to Paul D. Trokhan on Jan. 20,
1987; all of which are incorporated herein by reference.
In general, pattern densified webs are preferably prepared by
depositing a paper making furnish on a foraminous forming wire such
as a Fourdrinier wire to form a wet web and then juxtaposing the
web against an array of supports. The web is pressed against the
array of supports, thereby resulting in densified zones in the web
at the locations geographically corresponding to the points of
contact between the array of supports and the wet web. The
remainder of the web not compressed during this operation is
referred to as the high bulk field. This high bulk field can be
further dedensified by application of fluid pressure, such as with
a vacuum type device or a blow-through dryer. The web is dewatered,
and optionally predried, in such a manner so as to substantially
avoid compression of the high bulk field. This is preferably
accomplished by fluid pressure, such as with a vacuum type device
or blow-through dryer, or alternately by mechanically pressing the
web against an array of supports wherein the high bulk field is not
compressed. The operations of dewatering, optional predrying and
formation of the densified zones may be integrated or partially
integrated to reduce the total number of processing steps
performed. Subsequent to formation of the densified zones,
dewatering, and optional predrying, the web is dried to completion,
preferably still avoiding mechanical pressing. Preferably, from
about 8% to about 55% of the multi-layered tissue paper surface
comprises densified knuckles having a relative density of at least
125% of the density of the high bulk field.
The array of supports is preferably an imprinting carrier fabric
having a patterned displacement of knuckles which operate as the
array of supports which facilitate the formation of the densified
zones upon application of pressure. The pattern of knuckles
constitutes the array of supports previously referred to.
Imprinting carrier fabrics are disclosed in U.S. Pat. No.
3,301,746, Sanford and Sisson, issued Jan. 31, 1967, U.S. Pat. No.
3,821,068, Salvucci, Jr. et al ., issued May 21, 1974, U.S. Pat.
No. 3,974,025, Ayers, issued Aug. 10, 1976, U.S. Pat. No.
3,573,164, Friedberg et al., issued Mar. 30, 1971, U.S. Pat. No.
3,473,576, Amneus, issued Oct. 21, 1969, U.S. Pat. No. 4,239,065,
Trokhan, issued Dec. 16, 1980, and U.S. Pat. No. 4,528,239,
Trokhan, issued Jul. 9, 1985, all of which are incorporated herein
by reference.
Preferably, the furnish is first formed into a wet web on a
foraminous forming carrier, such as a Fourdrinier wire. The web is
dewatered and transferred to an imprinting fabric. The furnish may
alternately be initially deposited on a foraminous supporting
carrier which also operates as an imprinting fabric. Once formed,
the wet web is dewatered and, preferably, thermally predried to a
selected fiber consistency of between about 40% and about 80%.
Dewatering can be performed with suction boxes or other vacuum
devices or with blow-through dryers. The knuckle imprint of the
imprinting fabric is impressed in the web as discussed above, prior
to drying the web to completion. One method for accomplishing this
is through application of mechanical pressure. This can be done,
for example, by pressing a nip roll which supports the imprinting
fabric against the face of a drying drum, such as a Yankee dryer,
wherein the web is disposed between the nip roll and drying drum.
Also, preferably, the web is molded against the imprinting fabric
prior to completion of drying by application of fluid pressure with
a vacuum device such as a suction box, or with a blow-through
dryer. Fluid pressure may be applied to induce impression of
densified zones during initial dewatering, in a separate,
subsequent process stage, or a combination thereof.
Uncompacted, nonpattern-densified multi-layered tissue paper
structures are described in U.S. Pat. No. 3,812,000 issued to
Joseph L. Salvucci, Jr. and Peter N. Yiannos on May 21, 1974 and
U.S. Pat. No. 4,208,459, issued to Henry E. Becker, Albert L.
McConnell, and Richard Schutte on Jun. 17, 1980, both of which are
incorporated herein by reference. In general, uncompacted, non
pattern densified multi-layered tissue paper structures are
prepared by depositing a paper making furnish on a foraminous
forming wire such as a Fourdrinier wire to form a wet web, draining
the web and removing additional water without mechanical
compression until the web has a fiber consistency of at least 80%,
and creping the web. Water is removed from the web by vacuum
dewatering and thermal drying. The resulting structure is a soft
but weak high bulk sheet of relatively uncompacted fibers. Bonding
material is preferably applied to portions of the web prior to
creping.
The tissue paper web of the present invention may be creped or be
uncreped, as desired. An example of a method of making an uncreped,
through-air dried tissue paper product is described in European
Patent Application No. 0 677 612 A2 assigned to Kimberly-Clark
Corporation, published Oct. 18, 1995, and incorporated herein by
reference. Such uncreped, through-air dried structures are suitable
for the practice of this invention.
The multi-layered tissue paper web of this invention can be used in
any application where soft, absorbent multi-layered tissue paper
webs are required. Particularly advantageous uses of the
multi-layered tissue paper web of this invention are in toilet
tissue and facial tissue products. For example, two multi-layered
tissue paper webs of this invention can be ply-bonded to form 2-ply
facial or toilet tissue products.
Molecular Weight Determination
A. Introduction
The essential distinguishing characteristic of polymeric materials
is their molecular size. The properties which have enabled polymers
to be used in a diversity of applications derive almost entirely
from their macromolecular nature. In order to characterize fully
these materials it is essential to have some means of defining and
determining their molecular weights and molecular weight
distributions. It is more correct to use the term relative
molecular mass rather the molecular weight, but the latter is used
more generally in polymer technology. It is not always practical to
determine molecular weight distributions. However, this is becoming
more common practice using chromatographic techniques. Rather,
recourse is made to expressing molecular size in terms of molecular
weight averages.
B. Molecular weight averages
If we consider a simple molecular weight distribution which
represents the weight fraction (w.sub.i) of molecules having
relative molecular mass (M.sub.i), it is possible to define several
useful average values. Averaging carried out on the basis of the
number of molecules (N.sub.i) of a particular size (M.sub.i) gives
the Number Average Molecular Weight ##EQU1##
An important consequence of this definition is that the Number
Average Molecular Weight in grams contains Avogadro's Number of
molecules. This definition of molecular weight is consistent with
that of monodisperse molecular species, i.e. molecules having the
same molecular weight. Of more significance is the recognition that
if the number of molecules in a given mass of a polydisperse
polymer can be determined in some way then .sub.n, can be
calculated readily. This is the basis of colligative property
measurements.
Averaging on the basis of the weight fractions (W.sub.i) of
molecules of a given mass (M.sub.i) leads to the definition of
Weight Average Molecular Weights ##EQU2## .sub.w is a more useful
means for expressing polymer molecular weights than .sub.n since it
reflects more accurately such properties as melt viscosity and
mechanical properties of polymers and is therefor used in the
present invention.
Analytical and Testing Procedures
Analysis of the amount of biodegradable treatment chemicals used
herein or retained on tissue paper webs can be performed by any
method accepted in the applicable art.
A. Quantitative analysis for ester-functional quaternary ammonium
and polyhydroxy compounds
For example, the level of the ester-functional quaternary ammonium
compound, such as DiEster Di(Hydrogenated)Tallow DiMethyl Ammonium
Chloride (DEDHTDMAC) (i.e., ADOGEN DDMC.RTM.), retained by the
tissue paper can be determined by solvent extraction of the
DEDHTDMAC by an organic solvent followed by an anionicationic
titration using Dimidium Bromide as indicator; the level of the
polyhydroxy compound, such as PEG-400, can be determined by
extraction in an aqueous solvent such as water followed by gas
chromatography or colorimetry techniques to determine the level of
PEG-400 in the extract. These methods are exemplary, and are not
meant to exclude other methods which may be useful for determining
levels of particular components retained by the tissue paper.
B. Hydrophilicity (absorbency)
Hydrophilicity of multi-layered tissue paper refers, in general, to
the propensity of the multi-layered tissue paper to be wetted with
water. Hydrophilicity of multi-layered tissue paper may be somewhat
quantified by determining the period of time required for dry
multi-layered tissue paper to become completely wetted with water.
This period of time is referred to as "wetting time". In order to
provide a consistent and repeatable test for wetting time, the
following procedure may be used for wetting time determinations:
first, a conditioned sample unit sheet (the environmental
conditions for testing of paper samples are 23+1.degree. C. and
50+2% R.H. as specified in TAPPI Method T 402), approximately 43/8
inch.times.43/4 inch (about 11.1 cm.times.12 cm) of multi-layered
tissue paper structure is provided; second, the sheet is folded
into four (4) juxtaposed quarters, and then crumpled into a ball
approximately 0.75 inches (about 1.9 cm) to about 1 inch (about 2.5
cm) in diameter; third, the balled sheet is placed on the surface
of a body of distilled water at 23.+-.1.degree. C. and a timer is
simultaneously started; fourth, the timer is stopped and read when
wetting of the balled sheet is completed. Complete wetting is
observed visually.
Hydrophilicity characters of multi-layered tissue paper embodiments
of the present invention may, of course, be determined immediately
after manufacture. However, substantial increases in hydrophobicity
may occur during the first two weeks after the multi-layered tissue
paper is made: i.e., after the paper has aged two (2) weeks
following its manufacture. Thus, the wetting times are preferably
measured at the end of such two week period. Accordingly, wetting
times measured at the end of a two week aging period at room
temperature are referred to as "two week wetting times".
C. Biodegradable
Suitable substantially waterless self-emulsifiable biodegradable
chemical softening composition for use in the present invention are
biodegradable. As used herein, the term "biodegradability" refers
to the complete breakdown of a substance by microorganisms to
carbon dioxide, water, biomass, and inorganic materials. The
biodegradation potential can be estimated by measuring carbon
dioxide evolution and dissolved organic carbon removal from a
medium containing the substance being tested as the sole carbon and
energy source and a dilute bacterial inoculum obtained from the
supernatant of homogenized activated sludge. See Larson,
"Estimation of Biodegradation Potential of Xenobiotic Organic
Chemicals," Applied and Environmental Microbiology, Volume 38
(1979), pages 1153-61, which describes a suitable method for
estimating biodegradability. Using this method, a substance is said
to be readily biodegradable if it has greater than 70% carbon
dioxide evolution and greater than 90% dissolved organic carbon
removal within 28 days. The softeners used in the present invention
meet such biodegradability criteria.
C. Density
The density of multi-layered tissue paper, as that term is used
herein, is the average density calculated as the basis weight of
that paper divided by the caliper, with the appropriate unit
conversions incorporated therein. Caliper of the multi-layered
tissue paper, as used herein, is the thickness of the paper when
subjected to a compressive load of 95 g/in.sup.2 (15.5
g/cm.sup.2).
D. Lint
Dry lint
Dry lint can be measured using a Sutherland Rub Tester, a piece of
black felt, a four pound weight and a Hunter Color meter. The
Sutherland tester is a motor-driven instrument which can stroke a
weighted sample back and forth across a stationary sample. The
piece of black felt is attached to the four pound weight. The
tester then rubs or moves the weighted felt over a stationary issue
sample for five strokes. The Hunter Color L value of the black felt
is determined before and after rubbing. The difference in the two
Hunter Color readings constitutes a measurement of dry linting.
Other methods known in the prior arts for measuring dry lint also
can be used.
Wet lint
A suitable procedure for measuring the wet linting property of
tissue samples is described in U.S. Pat. No. 4,950,545; issued to
Walter et al., on Aug. 21, 1990, and incorporated herein by
reference. The procedure essentially involves passing a tissue
sample through two steel rolls, one of which is partially submerged
in a water bath. Lint from the tissue sample is transferred to the
steel roll which is moistened by the water bath. The continued
rotation of the steel roll deposits the lint into the water bath.
The lint is recovered and then counted. See col. 5, line 45--col.
6, line 27 of the Walter et al. patent. Other methods known in the
prior art for measuring wet lint also can be used.
Optional Ingredients
Other chemicals commonly used in paper making can be added to the
biodegradable chemical softening composition described herein, or
to the paper making furnish so long as they do not significantly
and adversely affect the softening, absorbency of the fibrous
material, and enhancing actions of the biodegradable chemical
softening composition.
For example, surfactants may be used to treat the multi-layered
tissue paper webs of the present invention. The level of
surfactant, if used, is preferably from about 0.01% to about 2.0%
by weight, based on the dry fiber weight of the multi-layered
tissue paper. The surfactants preferably have alkyl chains with
eight or more carbon atoms. Exemplary anionic surfactants are
linear alkyl sulfonates, and alkylbenzene sulfonates. Exemplary
nonionic surfactants are alkylglycosides including alkylglycoside
esters such as Crodesta SL-40 which is available from Croda, Inc.
(New York, N.Y.); alkylglycoside ethers as described in U.S. Pat.
No. 4,011,389, issued to W. K Langdon, et al. on Mar. 8, 1977; and
alkylpolyethoxylated esters such as Pegosperse 200 ML available
from Glyco Chemicals, Inc. (Greenwich, Conn.) and IGEPAL RC-520
available from Rhone Poulenc Corporation (Cranbury, N.J.).
The above listings of optional chemical additives is intended to be
merely exemplary in nature, and are not meant to limit the scope of
the invention.
The following examples illustrate the practice of the present
invention but are not intended to be limiting thereof.
EXAMPLE 1
The purpose of this example is to illustrate a method that can be
used to make-up a substantially waterless self-emulsifiable
biodegradable chemical softener composition comprising a mixture of
DiEster Di(Touch Hardened)Tallow DiMethyl Ammonium Chloride
(DEDTHTDMAC) and Polyoxyethylene Glycol 400 (PEG-400).
A waterless self-emulsifiable biodegradable chemical softener
composition is prepared according to the following procedure: 1. An
equivalent weight of DEDTHTDMAC and PEG-400 is weighed separately;
2. PEG is heated up to about 66.degree. C. (150.degree. F.); 3.
DEDTHTDMAC is dissolved in the PEG to form a melted solution at
about 66.degree. C. (150.degree. F.); 4. Adequate mixing is
provided to form a homogenous mixture of DEDTHTDMAC in PEG; 5. The
homogenous mixture of (4) is cooled down to a solid form at room
temperature.
The substantially waterless self-emulsifiable biodegradable
chemical softener composition of (5) can be pre-mixed (steps 1-5
above) at the chemical supplier (e.g. Sherex company of Dublin,
Ohio) and then economically shipped to the ultimate users of the
biodegradable chemical softening composition where it can then be
diluted to the desired concentration.
EXAMPLE 2
The purpose of this example is to illustrate a method using blow
through drying and layered paper making techniques to make soft,
absorbent and lint resistance toilet multi-layered tissue paper
treated with a chemical softener composition comprising DiEster
Di(Touch Hardened)Tallow DiMethyl Ammonium Chloride (DEDTHTDMAC)
and a Polyoxyethylene Glycol 400 (PEG-400) and a temporary wet
strength resin.
A pilot scale Fourdrinier paper making machine is used in the
practice of the present invention. First, the chemical softener
composition is prepared according to the procedure in Example 1
wherein the homogenous premix of DEDTHTDMAC and polyhydroxy
compounds in solid state is re-melted at a temperature of about
66.degree. C. (150.degree. F.). The melted mixture is then
dispersed in a conditioned water tank (pH.about.3,
Temperature.about.66.degree. C.) to form a sub-micron vesicle
dispersion. The particle size of the vesicle dispersion is
determined using an optical microscopic technique. The particle
size range is from about 0.1 to 1.0 micron.
Second, a 3% by weight aqueous slurry of NSK is made up in a
conventional re-pulper. The NSK slurry is refined gently and a 2%
solution of the temporary wet strength resin (i.e. National starch
78-0080 marketed by National Starch and Chemical corporation of
New-York, N.Y.) is added to the NSK stock pipe at a rate of 0.75%
by weight of the dry fibers. The adsorption of the temporary wet
strength resin onto NSK fibers is enhanced by an in-line mixer. The
NSK slurry is diluted to about 0.2% consistency at the fan
pump.
Third, a 3% by weight aqueous slurry of Eucalyptus fibers is made
up in a conventional re-pulper. A 2% solution of the temporary wet
strength resin (i.e. National starch 78-0080 marketed by National
Starch and Chemical corporation of New-York, N.Y.) is added to the
Eucalyptus stock pipe before the stock pump at a rate of 0.1% by
weight of the dry fibers; and a 1% solution of the biodegradable
chemical softener mixture is added to the Eucalyptus stock pipe
before the in-line mixer at a rate of 0.2% by weight of the dry
fibers. The Eucalyptus slurry is diluted to about 0.2% consistency
at the fan pump.
The treated furnish mixture (30% of NSK/70% of Eucalyptus) is
layered in the head box and deposited onto a Fourdrinier wire to
form an embryonic web. Dewatering occurs through the Fourdrinier
wire and is assisted by a deflector and vacuum boxes. The
Fourdrinier wire is of a 5-shed, satin weave configuration having
84 machine-direction and 76 cross-machine-direction monofilaments
per inch, respectively. The embryonic wet web is transferred from
the photo-polymer wire, at a fiber consistency of about 15% at the
point of transfer, to a photo-polymer fabric having 562 Linear
Idaho cells per square inch, 40 percent knuckle area and 9 mils of
photo-polymer depth. Further de-watering is accomplished by vacuum
assisted drainage until the web has a fiber consistency of about
28%. The patterned web is pre-dried by air blow-through to a fiber
consistency of about 65% by weight. The web is then adhered to the
surface of a Yankee dryer with a sprayed creping adhesive
comprising 0.25% aqueous solution of Polyvinyl Alcohol (PVA). The
fiber consistency is increased to an estimated 96% before dry
creping the web with a doctor blade. The doctor blade has a bevel
angle of about 25 degrees and is positioned with respect to the
Yankee dryer to provide an impact angle of about 81 degrees; the
Yankee dryer is operated at about 800 fpm (feet per minute) (about
244 meters per minute). The dry web is formed into a roll at a
speed of 700 fpm (214 meters per minutes).
The web is converted into a one ply multi-layered tissue paper
product. The multi-layered tissue paper has about 18 #/3M Sq Ft
basis weight, contains about 0.2% of the biodegradable chemical
softener mixture and about 0.3% of the temporary wet strength
resin. Importantly, the resulting multi-layered tissue paper is
soft, absorbent, has good lint resistance and is suitable for use
as facial and/or toilet tissues.
EXAMPLE 3
The purpose of this example is to illustrate a method using a blow
through drying paper making technique to make soft, absorbent and
lint resistance toilet multi-layered tissue paper treated with a
chemical softener composition comprising DiEster Di(Touch
Hardened)Tallow DiMethyl Ammonium Chloride (DEDTHTDMAC) and a
polyhydroxy compound (PEG-400); and a dry strength additive
resin.
A pilot scale Fourdrinier paper making machine is used in the
practice of the present invention. First, the chemical softener
composition is prepared according to the procedure in Example 1
wherein the homogenous premix of DEDTHTDMAC and polyhydroxy
compound in solid state is re-melted at a temperature of about
66.degree. C. (150.degree. F.). The melted mixture is then
dispersed in a conditioned water tank (pH.about.3,
Temperature.about.66.degree. C.) to form a sub-micron vesicle
dispersion. The particle size of the vesicle dispersion is
determined using an optical microscopic technique. The particle
size range is from about 0.1 to 1.0 micron.
Second, a 3% by weight aqueous slurry of NSK is made up in a
conventional re-pulper. The NSK slurry is refined gently and a 2%
solution of the dry strength resin (i.e. Acco.RTM. 711 marketed by
American Cyanamid company of Fairfield, Ohio) is added to the NSK
stock pipe at a rate of 0.2% by weight of the dry fibers. The
adsorption of the dry strength resin onto NSK fibers is enhanced by
an in-line mixer. The NSK slurry is diluted to about 0.2%
consistency at the fan pump.
Third, a 3% by weight aqueous slurry of Eucalyptus fibers is made
up in a conventional re-pulper. A 2% solution of the dry strength
resin (i.e. Acco.RTM. 711 marketed by American Cyanamid company of
Fairfield, Ohio) is added to the Eucalyptus stock pipe before the
stock pump at a rate of 0.1% by weight of the dry fibers; and a 1%
solution of the biodegradable chemical softener mixture is added to
the Eucalyptus stock pipe before the in-line mixer at a rate of
0.2% by weight of the dry fibers. The Eucalyptus slurry is diluted
to about 0.2% consistency at the fan pump.
The treated furnish mixture (30% of NSK/70% of Eucalyptus) is
blended in the head box and deposited onto a Fourdrinier wire to
form an embryonic web. Dewatering occurs through the Fourdrinier
wire and is assisted by a deflector and vacuum boxes. The
Fourdrinier wire is of a 5-shed, satin weave configuration having
84 machine-direction and 76 cross-machine-direction monofilaments
per inch, respectively. The embryonic wet web is transferred from
the photo-polymer wire, at a fiber consistency of about 15% at the
point of transfer, to a photo-polymer fabric having 562 Linear
Idaho cells per square inch, 40 percent knuckle area and 9 mils of
photo-polymer depth. Further de-watering is accomplished by vacuum
assisted drainage until the web has a fiber consistency of about
28%. The patterned web is pre-dried by air blow-through to a fiber
consistency of about 65% by weight. The web is then adhered to the
surface of a Yankee dryer with a sprayed creping adhesive
comprising 0.25% aqueous solution of Polyvinyl Alcohol (PVA). The
fiber consistency is increased to an estimated 96% before the dry
creping the web with a doctor blade. The doctor blade has a bevel
angle of about 25 degrees and is positioned with respect to the
Yankee dryer to provide an impact angle of about 81 degrees; the
Yankee dryer is operated at about 800 fpm (feet per minute) (about
244 meters per minute). The dry web is formed into roll at a speed
of 700 fpm (214 meters per minutes).
The web is converted into a one ply multi-layered tissue paper
product. The multi-layered tissue paper has about 18 #/3M Sq Ft
basis weight, contains about 0.1% of the biodegradable chemical
softener mixture and about 0.2% of the dry strength resin.
Importantly, the resulting multi-layered tissue paper is soft,
absorbent, has good lint resistance and is suitable for use as
facial and/or toilet tissues.
EXAMPLE 4
The purpose of this example is to illustrate a method using a
conventional drying paper making technique to make soft, absorbent
and lint resistance toilet multi-layered tissue paper treated with
a chemical softener composition comprising DiEster Di(Touch
Hardened)Tallow DiMethyl Ammonium Chloride (DEDTHTDMAC) and a
Polyoxyethylene Glycol 400 (PEG-400), a dry strength additive and a
cationic polyacrylamide additive resin (Percol.RTM. 175) as a
retention aid.
A pilot scale Fourdrinier paper making machine is used in the
practice of the present invention. First, the chemical softener
composition is prepared according to the procedure in Example 1
wherein the homogenous premix of DEDTHTDMAC and PEG-400 in solid
state is dispersed in a conditioned water tank (pH.about.3,
Temperature.about.66.degree. C.) to form a sub-micron vesicle
dispersion. The particle size of the vesicle dispersion is
determined using an optical microscopic technique. The particle
size range is from about 0.1 to 1.0 micron.
Second, a 3% by weight aqueous slurry of NSK is made up in a
conventional re-pulper. The NSK slurry is refined gently and a 2%
solution of the dry strength resin (i.e. Acco.RTM. 711 marketed by
American Cyanamid company of Wayne, N.J.) is added to the NSK stock
pipe at a rate of 0.2% by weight of the dry fibers. The adsorption
of the dry strength resin onto NSK fibers is enhanced by an in-line
mixer. The NSK slurry is diluted to about 0.2% consistency at the
fan pump.
Third, a 3% by weight aqueous slurry of Eucalyptus fibers is made
up in a conventional re-pulper. A 1% solution of the biodegradable
chemical softener mixture is added to the Eucalyptus stock pipe
before the stock pump at a rate of 0.2% by weight of the dry
fibers; and a 0.05% solution of Percol.RTM. 175 is added to the
Eucalyptus layers before the fan pump at a rate of 0.05% by weight
of the dry fibers. The adsorption of the biodegradable chemical
softener mixture to Eucalyptus fibers can be enhanced by an in-line
mixer. The Eucalyptus slurry is diluted to about 0.2% consistency
at the fan pump.
The treated furnish mixture (30% of NSK/70% of Eucalyptus) is
layered in the head box and deposited onto a Fourdrinier wire to
form an embryonic web. Dewatering occurs through the Fourdrinier
wire and is assisted by a deflector and vacuum boxes. The
Fourdrinier wire is of a 5-shed, satin weave configuration having
84 machine-direction and 76 cross-machine-direction monofilaments
per inch, respectively. The embryonic wet web is transferred from
the Fourdrinier wire, at a fiber consistency of about 15% at the
point of transfer, to a conventional felt. Further de-watering is
accomplished by vacuum assisted drainage until the web has a fiber
consistency of about 35%. The web is then adhered to the surface of
a Yankee dryer. The fiber consistency is increased to an estimated
96% before dry creping the web with a doctor blade. The doctor
blade has a bevel angle of about 25 degrees and is positioned with
respect to the Yankee dryer to provide an impact angle of about 81
degrees; the Yankee dryer is operated at about 800 fpm (feet per
minute) (about 244 meters per minute). The dry web is formed into
roll at a speed of 700 fpm (214 meters per minutes).
Two plies of the web are formed into multi-layered tissue paper
products and laminating them together using ply bonded technique.
The multi-layered tissue paper has about 23 #/3M Sq. Ft. basis
weight, contains about 0.1% of the biodegradable chemical softener
mixture, about 0.1% of the dry strength resin and about 0.05% of
the retention aid resin. Importantly, the resulting multi-layered
tissue paper is soft, absorbent, has good lint resistance and is
suitable for use as a facial and/or toilet tissues.
EXAMPLE 5
The purpose of this example is to illustrate a method using a blow
through drying and layered paper making techniques to make soft,
absorbent and lint resistance facial multi-layered tissue paper
treated with a chemical softener composition comprising DiEster
Di(Touch Hardened)Tallow DiMethyl Ammonium Chloride (DEDTHTDMAC)
and a Polyoxyethylene Glycol 400 (PEG-400), a permanent wet
strength resin and a retention aid (Percol.RTM. 175).
A pilot scale Fourdrinier paper making machine is used in the
practice of the present invention. First, the chemical softener
composition is prepared according to the procedure in Example 1
wherein the homogenous premix of DEDTHTDMAC and polyhydroxy
compounds in solid state is re-melted at a temperature of about
66.degree. C. (150.degree. F.). The melted mixture is then
dispersed in a conditioned water tank (pH.about.3,
Temperature.about.66.degree. C.) to form a sub-micron vesicle
dispersion. The particle size of the vesicle dispersion is
determined using an optical microscopic technique. The particle
size range is from about 0.1 to 1.0 micron.
Second, a 3% by weight aqueous slurry of NSK is made up in a
conventional re-pulper. The NSK slurry is refined gently and a 2%
solution of the permanent wet strength resin (i.e. Kymene.RTM. 557H
marketed by Hercules Incorporated of Wilmington, Del.) is added to
the NSK stock pipe at a rate of 1 % by weight of the dry fibers.
The adsorption of the temporary wet strength resin onto NSK fibers
is enhanced by an in-line mixer. The NSK slurry is diluted to about
0.2% consistency at the fan pump.
Third, a 3% by weight aqueous slurry of Eucalyptus fibers is made
up in a conventional re-pulper. A 1% solution of the biodegradable
chemical softener mixture is added to the Eucalyptus stock pipe
before the in-line mixer at a rate of 0.2% by weight of the dry
fibers; and a 0.5% solution of Percol.RTM. 175 is added to the
Eucalyptus layers before the fan pump at a rate of 0.05% by weight
of the dry fibers. The Eucalyptus slurry is diluted to about 0.2%
consistency at the fan pump.
The treated furnish (50% of NSK/50% of Eucalyptus) is layered in
the head box and deposited onto a Fourdrinier wire to form an
embryonic web. Dewatering occurs through the Fourdrinier wire and
is assisted by a deflector and vacuum boxes. The Fourdrinier wire
is of a 5-shed, satin weave configuration having 84
machine-direction and 76 cross-machine-direction monofilaments per
inch, respectively. The embryonic wet web is transferred from the
photo-polymer wire, at a fiber consistency of about 15% at the
point of transfer, to a photo-polymer fabric having 711 Linear
Idaho cells per square inch, 40 percent knuckle area and 9 mils of
photo-polymer depth. Further de-watering is accomplished by vacuum
assisted drainage until the web has a fiber consistency of about
28%. The patterned web is pre-dried by air blow-through to a fiber
consistency of about 65% by weight. The web is then adhered to the
surface of a Yankee dryer with a sprayed creping adhesive
comprising 0.25% aqueous solution of Polyvinyl Alcohol (PVA). The
fiber consistency is increased to an estimated 96% before dry
creping the web with a doctor blade. The doctor blade has a bevel
angle of about 25 degrees and is positioned with respect to the
Yankee dryer to provide an impact angle of about 81 degrees; the
Yankee dryer is operated at about 800 fpm (feet per minute) (about
244 meters per minute). The dry web is formed into a roll at a
speed of 700 fpm (214 meters per minutes).
The web is converted into a two ply multi-layered facial tissue
paper. The multi-layered tissue paper has about 21#/3M Sq Ft basis
weight, contains about 1% of the permanent wet strength resin,
about 0.2% of the biodegradable chemical softener mixture and about
0.05% of the retention aid resin. Importantly, the resulting
multi-layered tissue paper is soft, absorbent, has good lint
resistance and is suitable for use as facial tissues.
* * * * *